NAS200 can't see new disk in bay1

Hi,
i have a problem with my nas200. After replace a harddrive from 160GB to 250GB they don't recognize it. The disk led on nas200 have not a led light. But the disk ist recognized in bay 2. Wher is the problem?

thanks for replay. The problem is when i switch disk from bay2 to bay1 then nas200 donst see it in bay1. I have a two disk : bay1- 140GB bay2 - 400GB. When i switch the disk in bay1 with new disk 250GB then the nas200 start very long and after that he don not see new disk. I have tried this switching yesterday all day. Is ir possible that may nas dont see in bay1 250GB disk sata2?